Question #7259d

• There is a buffer region in the strong base / weak acid titration curve where the #"pH"# rises slowly, but not the strong base / strong acid titration.
• For the strong base / weak acid titration curve, we do have a half-equivalence point where #"pH"# #~~# #"pKa"#, but that relationship does not hold true for the strong base / strong acid titration curve.
• #"pH"# at the equivalence point is greater than #7# for the strong base / weak acid titration and equal to #7# for the strong base / strong acid titration.

The main qualities (without identified differences yet) you should expect from each kind of titration curve are:

Both curves

• Starting #"pH"# of what is being titrated (what the titrant from the burette is being dripped into) is less than #7# (after the equivalence point).
• End #"pH"# of what is being titrated is greater than #7# (after the equivalence point).

Strong base into strong acid

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• There is no buffer region on the way to the equivalence point, because we need a weak acid / conjugate base or weak base / conjugate acid combination to have this. This lack of a buffer region is seen as a simple flat rise.
• There is a half-equivalence point, but the #"pH"# is simply given by the concentration of #"H"^(+)# in the solution, and bears no relationship to the #"pKa"# of the acid.
• #"pH"# at the equivalence point is exactly #7# (exact neutralization of all #"H"^(+)# and #"OH"^(-)# that are not from water).

Strong base into weak acid

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• There is a buffer region on the way to the equivalence point where the #"pH"# increases slowly. This is seen as an initial "hill" into a flat rise.
• There is a half-equivalence point, i.e. half the volume of the equivalence point, which has #"pH"# #~~# #"pKa"# (from the Henderson-Hasselbalch equation), where #"pKa" = -logK_a# and #K_a# is the acid dissociation constant.
• #"pH"# at the equivalence point is greater than #7#. You can think of it as the strong base "dominating" the resultant #"pH"# at that point.

DIFFERENCES

In the end, we can summarize the following differences:

• There is a buffer region in the strong base / weak acid titration curve where the #"pH"# rises slowly, but not the strong base / strong acid titration.
• For the strong base / weak acid titration curve, we do have a half-equivalence point where #"pH"# #~~# #"pKa"#, but that relationship does not hold true for the strong base / strong acid titration curve.
• #"pH"# at the equivalence point is greater than #7# for the strong base / weak acid titration and equal to #7# for the strong base / strong acid titration.